[CentOS] MySQL max clustering package?

Neil Aggarwal neil at JAMMConsulting.com
Wed Mar 17 18:07:32 UTC 2010


Alex:

> Do you mean that a separate job, iterates the orders, accumulates the
> real ordered quantity and subtracts it from some "initial quantity" in
> order to produce available quantity?

There are a few things we do:
1. When we place an order, we commit the order to the database in
	a transaction.
2. In a separate transaction, we reduce the qty available of the
	product by the amounts ordered.  This transaction may be
	a conflict with other transactions.  That is OK.
3. The inventory management system keeps the master inventory
	of the products.  We have a continuous job that pulls the
	latest updates to the inventory and feeds those updates
	back to the web database.

So, even if an inventory number is wrong for a short time, it will
be updated to an accurate number soon.

> What do you do in cases where you have oversold a product. I mean when
> the "ordered quantity"  got bigger than the "available quantity" due
> to a conflict in available quantity field? I assume that the system
> sends an email to the warehouse to increase additionally the quantity
> of that product?

If we oversell a product, we are going to either have to get more
pronto or tell the customer we can't deliver it.  The inventory 
numbers are updated often enough that we do not encounter it often.

> Could you describe a case where a transaction has failed , and how you
> deal with it?

If a transaction fails on one endpoint, we try it against another
endpoint.  If it still fails, it depends on what the transaction
was for.  If it is not urgent (Like updating an inventory number)
we send ourselves and alert and drop the transaction.  If it is
urgent, we notify the customer there was an error and send ourselves
an alert.  This happens very rarely.

We also have monitoring on the state of the replication endpoints
to make sure they are still active and are not having a problem
communicating to the master.

I hope this helps,
	Neil

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